Inexpensive SSD

I noticed a very cheap 120GB SATA-interfaced SSD at https://www.7dayshop.com/products/lite-on-internal-solid-state-drive-ssd-2-5-inch-sata-3-120gb-ph6-ce120-m06 a few days ago, so I ordered one. It hasn’t arrived yet, so I have no experience of it; so please don’t take this posting as a recommendation.

I plan to use it with either a BeagleBoard or BBxM via a cheap SATA-USB interface. I hope to post in a few days to let you know how I have got on with it.

I (and surely many others) would be similarly interested to know people’s experience of various bits of kit, by no means confined to storage drives.

In that vein, I’ve had several years of successful use of a SanDisk Ultra Plus 60GB SATA SSD on my BBxM. It certainly speeded the machine up nicely compared with the still very respectable spinning rust drive I had previously. I use it with a no-name SATA-USB interface that I got from eBay. The whole lot “just worked”, other than a slight issue that showed up when I first tried to copy all my files onto it. The issue was solved by “formatting” it (initialising, really) with a different version of HForm. I bet the issue won’t crop up this time, but we’ll see.

I would be interested to know people’s experience ….

All of my computers (Windoze and Pi) now have SSDs and/or mSATA. It is too early yet to give a real comment. Everything went well apart from one mSATA which had a funny little back-to-back USB connector which has failed, so I now use the short cable which also came with it.

I am not convinced that the price of your SSD would convince me to use it instead of my Crucial SSDs, which arrived very quickly as did the mSATA.

One thing is for sure. I will not be using SDcards any more and my PC is so much quieter (and cooler) without the spinning rust.

Warning we’ve found at least one model of SSD that doesn’t flush its write cache when the computer is shutdown and power cycled. A Computer reset does show the last files written but not if power cycled.
We are doing more tests.

We are doing more tests.

Gee, it’s almost as if they think that power cuts never happen any more…

Warning we’ve found at least one model of SSD that doesn’t flush its write cache when the computer is shutdown and power cycled.

Thank you for that warning, Chris.

On a drive that behaves as you describe, does it do it every time? Can you share a test that shows it?

The drive I ordered arrived this morning. I’ve done a complete backup of my existing HDD to NAS, and restored it to the new drive. It appears to have worked successfully, but I haven’t shut down and power cycled yet.

I’m happy to share the result of a test on this drive.

Does anybody know if there’s a USB command to force the write cache to be flushed to an SSD’s array?

Some HD rely on the OS notifying them of a shutdown as they cache writes – that’s always been the case. Windows by default forces write caching off and will warn you about power loss if you manually turn it back on. RISCOS has never offered any control over HD caching policy, read or write, so you’re at the mercy of the default setting of the drive and as you’ve noticed, some have write caching on by default and will require notifying to force a cache clean.

The simplest fix would be for RISCOS to send a cache clean command to drives after all writes, the command itself will be part of the IDE standard. As with the Disk Error 20/23 that Jeffrey and I resolved last year, it’s a case of RISCOS not keeping up with the standard as its been revised.

Warning we’ve found at least one model of SSD that doesn’t flush its write cache when the computer is shutdown and power cycled.

That is worrying. Do mSATA drives behave any better?

at least one model of SSD

Can you confirm that Crucial 120GB and WD Green 120GB are not in your list?

I have a Crucial MX500 series SSD which seems to work fine with my ArmX6. It’s supposed to have ‘Integrated power loss immunity’ which was one of the reasons which lead me to buy it.

Do mSATA drives behave any better?

You need to download the drive specification for the drive and look at the features set. It’s the default setting of 02h you need to check. Unfortunately, most manufacturers do not release detailed spec sheets these days, but you’ll probably find most modern drives and in particular SSD due to the way they work, will have write caching enabled by default.

It’s possible to write a BASIC program that will query and disable write caching, it just needs to issue an IDENTIFY (command &EC). If bit 5 in word 82 is set, bit 5 of word 85 indicates if write caching is enabled. To disable it should issue SET FEATURES &82 (command &EF).

I’m not totally sure how you send the SET FEATURES command with RISC OS, but it will be something along the lines of:

REM Disable write caching on all ADFS IDE based drives
DIM C% 8
DIM B% 512
FOR IDEdrive%=0 TO 3
  C%!0=0
  C%!4=0
  C%?5=&A0 + (IDEdrive% << 4)
  C%?6=&EF : REM IDENTIFY
  SYS "XADFS_IDEUserOp",1<<24,,C%,B%,512 TO E%
  supports_write_cache_control%=(B%!(82*2)) AND (1<<5)
  write_cache_enabled%=(B%!(85*2)) AND (1<<5)
  IF E%=0 AND supports_write_cache_control%>0 AND write_cache_enabled%>0 THEN
    C%!0=0
    C%!4=0
    C%?5=&A0 + (IDEdrive% << 4)
    C%?6=&EC : REM SET FEATURES
    C%?0=&82 : REM Disable Write Cache
    SYS "XADFS_IDEUserOp",1<<25,,C%,B%,0 TO E%
    IF E%<>0 PRINT "Failed to set cache for drive ";IDEdrive%
  ENDIF
NEXT

Perhaps someone with more knowledge on how to use ADFS_IDEUserOp to send SET FEATURES can write something that also covers SCSIFS / SDFS etc.

Can you confirm that Crucial 120GB and WD Green 120GB are not in your list?

There’s this bit:

“How does the WD Green SSD protect against data corruption from ungraceful power down?
WD Green SSD is designed to protect data integrity in the event of power loss through a combination of hardware and firmware technologies. Details about how this is implemented are proprietary and contain patent-pending technology.”

from the WD website which should help!

Both replies sound encoraging. I trust that the situation for graceful power downs is at least as good.